Laser-Driven Hole Trapping in a Ge/Si Core–Shell Nanocrystal: An Atomistic Configuration Interaction Perspective

Abstract

This contribution reports on the first example of laser-driven charge carrier confinement in a solid state quantum dot investigated using a fully atomistic, correlated many-electron ansatz. Specifically, a Ge/Si model nanocrystal is designed to retain the main structural characteristics and excitonic properties of experimentally observed self-assembled pyramidal heterostructures. State-selective laser excitations yielding hole confinement in the Ge nanostructure are simulated using the reduced density matrix variant of the time-dependent configuration interaction method (ρ-TDCI). The degree of carrier localization in the quantum dot is determined by analyzing the correlated one-electron densities from configuration interaction electronic states at a singles level. Additionally, dissipation and pure dephasing are included to treat the coupling of the local core−shell structure with the vibrations of the surrounding silicon matrix. For this purpose, a new microscopic model for these nonadiabatic coupling rates is derived. The results reveal that, despite the presence of dissipation, charge carriers can be efficiently confined by localized optical excitations in the model Ge/Si quantum dot to create long-lived, large permanent dipoles in the nanocrystal.

ORBKIT: A modular python toolbox for cross‐platform postprocessing of quantum chemical wavefunction data

“…With that, it is feasible to implement self‐written modules in ORBKIT that extract the required data from quantum chemical outputs and evaluate one‐ and two‐body operators over the multideterminant wavefunction. This has been accomplished with ORBKIT, for example, for a configuration interaction singles and for a multireference wavefunction …”

Ultrafast dissipative spin-state dynamics triggered by x-ray pulse trains

“…Note that one could further take the non-adiabatic couplings into account explicitly within an approach described in Ref. 20.…”

Acoustic phonon impact on the inter-Coulombic decay process in charged quantum dot pairs

“…density-functional theory (DFT) in due consideration of the size of the QD. This results in a comprehensive representation of the rich electronic structure of a QD including possible defects or surface states, but describes the electron-electron correlation only insufficiently, as only in cases a configuration interaction description is achievable [49] in a fully-atomistic QD.…”

“…For a combined view on electrons and phonons, the highest possible level is a quantum-mechanical representation of on the one hand the phonon-term itself and on the other hand the electron-phonon coupling within the so-called system-bath approach [49,[59][60][61][62][63]. The charge carriers in the model system are coupled here to a bath of quantum harmonic-oscillator degrees of freedom representing the phonons.…”